Tuesday, September 25, 2012

Figure 1. The Violet or Purple Snail, a prey item of the non-tautonomical Blue Dragon nudibranch. I propose the new common name: Baggins Snail

If we accept the premise that snails are like Hobbits - you know, pretty much homebodies (insert rimshot here for the best snail pun ever!), and not overly predisposed to doing anything too hastily - Janthina janthina (Figure 1) is the Bilbo Baggins of snails. J. janthina is not content to trail unambitiously along the ground, or leaves, or rocks, or mud, or whatever. This snail FLIES! And it does this by making its own blimp (Figure 2). True they do so underwater, but to a regular old humdrum sea snail confined haul their shells across the substrate, this must look like magic.

The snail uses mucus to trap air from the surface into bubbles, making a raft that keeps them afloat. The raft is driven around by wind and surface currents, and the snail goes on undirected, upside-down walkabouts on the surface of the ocean - so, blimp might not be as apt as hot-air balloon, really.

How did the snail learn to fly then? It turns out this is kind of a cool story (1). The bubble raft is an adapted form of the egg mass. Lots of snails lay their eggs in mucus-y masses. So the theory goes that some ancestor of this snail ended making egg masses with air trapped in them, which was good for the baby snails since they got dispersed, and ultimately the snails themselves started floating and now both sexes have the bubble-making-skillz, which are no longer directly related to making eggs. There are other adaptations that make them good at a sea-faring life, too (Figure 3). The shell is flat and thin(2) - which keeps it from sinking fast, and it's counter-shaded (dark on top, light on bottom) to make it harder to for predators to see.

Figure 3.Janthina janthina is well adapted to a flying lifestyle.

Why is it good to be in the pleuston(3)? Because it's delicious! J. janthina float along waiting to bump into delicious tautonomical prey: Velella velella

OMG! IT'S A TAUTONOMICAL FOOD CHAIN!!!

And that topic will be covered ... Next time, on Species species of the Week week.

(2) Most land snails have super thin shells, because shells are heavy to carry on land. But marine snails often have thick shells, because it's easier to carry thick shells under water, and there's some nasty crabs out there that would like nothing better than escargot.

(3) Wait, what's the pleuston, again? Well it's like the neuston, only for the big guys.

It turns out I was kind of serious about Mollusk Muzik series. Relevant songs have started popping into in my head recently. This whole thing kind of reminds me of that sketch they would do on Whose Line Is It Anyway? Whatever, I sort of liked that show. So here's Molluk Muzik #2 (+ Bonus B-side at the end of the post).Two out of the three title characters here are mollusks, and the other is one of my favorites:

Tuesday, September 18, 2012

I'm sure you've heard the conspiracy theory that sea slugs are involved in a major trans-species arms smuggling operation. Well, your humble narrator has done some investigative journalism for which she is completely unqualified and can tell you, the rumors are true. That's why I'm cheating today, starting a Species species of the Week week with a nudibranch that's not even close to a tautonym (2). Here is the culprit:

Blue Dragon

Glaucus atlanticus(1)

Figure 1.Glaucus atlanticus - the Blue Dragon (nudibranch). Holy Daenerys Targaryen, Batman! Am I right?! This thing is crazy, and if your heart doesn't explode just a little bit when you see this and contemplate that you share the earth with this creature, well ... I can only sputter my disbelief. Credit where credit is due.

Ok, so it looks cool, fine. But why does it deserve the [ahem, rather distinguished] honor of being a Species species of the Week week (weak?) when it's not even a tautonym (but see (2))?! Well, there was a passage in the Wikipedia entry:

Did you catch that? Almost every major prey item for this nudibranch is a tautonym (and Physalia physalis is just obnoxiously close - what a jerk)! Now I'm not saying that the diet of this slug is explained by the possession of a highly sophisticated taste - if I do say so myself - in grammar. For one, though I admittedly haven't done the research to back this up, I feel like it's safe to assume the emergence of slug's diet predates the naming of these prey species. But still...what are the odds? Really, I'd love to know what the odds are if anyone is patient enough to figure that out. In the next few tautonym posts (3), I'll cover a few of the double-named prey of the Blue Dragon - except definitely not that tease Physalia physalis.

But now back to the arms smuggling operation...

So, of course I'm all fixated on the improbability of an almost exclusively tautonomical diet, when I am reminded that what's even cooler, at least to most people, is that this diet is also the slug's defense. When the slug consumes jellies, it also eats the stinging cells (Figure 2). The slug then puts these cnidocytes into its own flesh (the cerata, specifically, which are the long finger-like projections that make this slug look so flamboyant). Anything that tries to attack the slug gets stung.

Figure 2. This is why it hurts, y'all. I know, my eyes just glaze over too when I see diagrams in the pastel color palette of academic textbooks (haven't they figured that out yet?). But this really is one of the better diagrams of how Cnidocytes work - terrifying.

So the slug has basically stolen poisoned harpoons from the jellies and incorporated them into it's own body so it becomes super-invulnerable. This, of course, reeks of Hollywood script possibilities (whoops, it appears I've been scooped. SPOILER ALERT: it doesn't end well for the invulnerable trans-species defense idea). Here is a National Geographic clip demonstrating the awesomeness of the Blue Dragon (4). There is, of course, a word for this process of stealing cnidocytes and deploying them against your enemies: Bioterrorism. No, well maybe, but the real word is Kleptocnidae.

(2) G. atlanticus was, however, the first (of only two) species named in the genus Glaucus, so according to my theory of tautonyms, it could have theoretically been Glaucus glaucus. And, frankly, if I'm going to editorialize here, atlanticus is a misleading species name (though hardly the only one) as the distribution of this species is not restricted to only the Atlantic ocean.

(3) Read: Until I get bored

(4) Editorial aside: Why does everyone now have these narrators that are so over the top for nature videos?! THis guy sounds so incredulous and has the dumbest comments. This is why I like David Attenborough and Marty Stouffer. They get it: nature sells itself and doesn't need a monster truck voice-over to make it exciting. That's another soapbox for another day though.

(5) Does Blogger have a reference management software? Rearranging these is getting rul old.